Scanning electron acoustic microscopy of residual stresses in ceramics - Theory and experimentThe paper presents a three-dimensional mathematical model of signal generation and contrast in brittle materials and uses the model to simulate the effect of residual stress fields on the scanning electron acoustic microscopy (SEAM)-generated electron acoustic signal. According to the model, a positive (tensile) strain produces an increase in the output signal, whereas a negative (compressive) strain produces a decrease in the ouput signal. Dark field contrast conditions occur at a chopping frequency at which V2 - V1 is greater than 0 (where V2 = V is the SEAM output in a region of residual stresses, and V1 is the output in a stress-free region of the sample). Under ideal conditions (maximum contrast) V1 approaches zero. It was found that tensile strains of the order 0.2-0.3 percent, possible in brittle materials, would produce a variation of the acoustic output signal of the order 10 nV (about 1 percent), well within the image contrast and signal processing capability of the SEAM electronics.
Document ID
19930071607
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Cantrell, John H. (Cambridge Univ., United Kingdom; NASA, Langley Research Center Hampton, VA, United States)
Qian, Menglu (Cambridge Univ. United Kingdom; Tongji Univ., Shanghai, China)